Acid stimulation is frequently used as a form of well intervention to restore production of a well to peak levels. Conventional methods for acid stimulation require use of large rigs and risers, while alternative systems can use remotely operable vehicles (ROVs), multi-service vessels (MSVs), or similar devices to access a wellhead in deep water, e.g., using coiled tubing ballasted with weight to ensure proper descent and stabilization over a working area. A significant length of conduit (e.g., 150 feet) is often necessary to ensure that the flying leads and connectors of the tubing can accommodate vessel heave and position deviation while allowing ample room for the front panel on the injection tool at the wellhead to be accessed.
When a well stimulation and/or an injection tool is engaged with a subsea well tree, other intervention operations are inhibited and/or rendered impossible, resulting in a significant downtime between well simulation and other intervention operations and necessitating the replacement and use of various equipment.
Conventional methods allow for acid injection via subsea umbilical/flying leads, e.g., through the installation of an acid tool that latches onto a tree via a tree running tool. Such methods allow for injection, but do not allow the wellbore to be accessed and/or only enable access via steel tubing and/or hosing. Thus, items having large outer diameters, such as an internal tree plug or wireline tools, cannot enter the wellbore. Essentially, wireline equipment cannot be operated within an umbilical or similar conduit due to the inherent physical constraints of the umbilical.
The limitation of equipment and methods that only permit injection of acid without having the ability to enter the well using wireline equipment contributes to operational downtime, as a separate pressure control assembly (e.g., a blowout preventer) is then needed to access the well with wireline equipment.
A need exists for systems and methods that enable both well stimulation operations and other intervention operations to be conducted, while minimizing the replacement of equipment and downtime therebetween, while maintaining at least two barrier valves to isolate the wellbore.
A further need exists for systems and methods that enable running of wireline equipment while providing at least two isolation barriers, the two or more barriers being closable to allow chemical injection to take place via placement of isolation barriers in an exterior portion (e.g., “wings”) of the system.
A need also exists for systems and methods that can be operated riglessly, or alternatively using only a small hoist and/or a multi-service vessel, eliminating the need for conventional rig and riser-based installation procedures. A lubricator and/or a “greasehead” can be used to create a seal during such rigless wireline operations.